Hey there, Eligobel.
Welcome to the Apple Support Communities! thanks for posting about the issues you're having with the keyboard on your Mac. We'd be glad to see how we can help.
It sounds like something may be happening with the keys themselves. Do you happen to recall anything occurring directly to the keyboard that could account for this behavior? This could be a drop of your MacBook Air or the spillage of liquid onto the keyboard directly. If not, you may be able to Use the Accessibility Keyboard on Mac as a short term fix. This is an onscreen keyboard that lets you use your Mac without using a physical keyboard.
Something else that may be applicable is the Keyboard Service Program for MacBook, MacBook Air, and MacBook Pro. Not all models are eligible, so be sure to check the page to see if yours may be. If none of the above helps to solve your issue, you may want to see about having your Mac inspected by a technician by following the guidance in Mac Service and Repair.
Take care.